Conventionally, constant temperature liquid baths for constantly keeping a temperature of an object are widely used, and in recent years, a heat supply apparatus having a thermo-module which adjusts temperature by Peltier effect is also used in the constant temperature liquid baths (see Japanese Patent Application Laid-open Nos. 7-308592 and 2000-75935 for example). Since the heat supply apparatus using the thermo-module can heat and cool only by changing a supply direction of current, it is easy to control the temperature and the heat supply apparatus can be reduced in size, and such a heat supply apparatus is extremely suitable for a small constant temperature bath.
When any heat supply apparatus is used in the constant temperature liquid bath, heat is exchanged with respect to the heat supply apparatus below the constant temperature liquid bath while usually taking characteristics of liquid to be controlled in temperature into account, a stirring impeller is provided on a bottom of the constant temperature liquid bath, or a magnetic rotor is rotated by a stirrer motor to stir the liquid, thereby constantly keeping the temperature of the liquid.
However, the liquid is mainly stirred in the circumferential direction and is not positively stirred in the vertical direction. Therefore, when an object which needs to be constantly kept in temperature is accommodated in a container (bottle) and immersed, there are problems that the vertical flow of liquid is largely hindered by the object, the stirring effect in an upper portion of the bath is deviated from a predicted range, a temperature distribution in the bath becomes extremely poor, and a temperature difference is generated between upper and lower portions in the bath. More specifically, when the container is not immersed, the temperature distribution is in a range of 0.1° C., but if the container is immersed, the temperature distribution becomes about 0.5° C.
For this reason, also in the constant temperature liquid bath using the thermo-module, it is desired that uniform liquid flow is always generated on a heat transfer surface of the thermo-module even if an article is immersed in the constant temperature liquid bath and the liquid flows in the entire bath and the liquid in the bath is stirred in an overall manner.